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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | PORTABILITY | AUTHORS | SEE ALSO | COLOPHON |
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form_fieldtype(3X) Library calls form_fieldtype(3X)
form_fieldtype - define validation-field types
#include <form.h>
FIELDTYPE *new_fieldtype(
bool (* const field_check)(FIELD *, const void *),
bool (* const char_check)(int, const void *));
int free_fieldtype(FIELDTYPE *fieldtype);
int set_fieldtype_arg(
FIELDTYPE *fieldtype,
void *(* const make_arg)(va_list *),
void *(* const copy_arg)(const void *),
void (* const free_arg)(void *));
int set_fieldtype_choice(
FIELDTYPE *fieldtype,
bool (* const next_choice)(FIELD *, const void *),
bool (* const prev_choice)(FIELD *, const void *));
FIELDTYPE *link_fieldtype(FIELDTYPE *type1,
FIELDTYPE *type2);
new_fieldtype
The function new_fieldtype creates a new field type usable for
data validation. Its parameters are function pointers:
field_check
This function checks the validity of an entered data string
whenever the user attempts to leave a field. It has two
arguments:
• The (FIELD *) argument is passed in so the validation
predicate can see the field's buffer, sizes and other
attributes.
• The second argument is an argument-block structure, about
which more below.
char_check
This function validates input characters as they are entered.
The form library passes it the character to be checked and a
pointer to an argument-block structure.
free_fieldtype
The free_fieldtype function frees the space allocated for a given
validation type by new_fieldtype.
set_fieldtype_arg
The function set_fieldtype_arg associates three storage-management
functions with a field type:
make_arg
This function is automatically applied to the list of
arguments you give set_field_type when attaching validation
to a field. It stores the arguments in an allocated
argument-block object which is used when validating input.
copy_arg
This function may be used by applications to copy argument-
blocks.
free_arg
Frees an argument-block structure.
You must supply the make_arg function. The other two are
optional: you may supply NULL for them. In this case, the form
library assumes that make_arg does not allocate memory but simply
loads the argument into a single scalar value.
set_fieldtype_choice
The form driver requests REQ_NEXT_CHOICE and REQ_PREV_CHOICE
assume that the possible values of a field form an ordered set,
and provide the forms user with a way to move through the set.
The set_fieldtype_choice function allows forms programmers to
define successor and predecessor functions for the field type.
These functions take the field pointer and an argument-block
structure as arguments.
link_fieldtype
The function link_fieldtype creates a new field type from the two
given types. They are connected by a logical “or”.
The pointer-valued routines return NULL on error. They set errno
according to their success:
E_OK The routine succeeded.
E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
E_SYSTEM_ERROR
System error occurred, e.g., malloc failure.
The integer-valued routines return one of the following codes on
error:
E_OK The routine succeeded.
E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
E_CONNECTED
The field is already connected to a form.
E_CURRENT
The field is the current field.
E_SYSTEM_ERROR
System error occurred (see errno(3)).
These routines emulate the System V forms library. They were not
supported on Version 7 or BSD versions.
Juergen Pfeifer. Manual pages and adaptation for new curses by
Eric S. Raymond.
curses(3X), form(3X), form_field_validation(3X)
This page is part of the ncurses (new curses) project.
Information about the project can be found at
⟨https://invisible-island.net/ncurses/ncurses.html⟩. If you have a
bug report for this manual page, send it to bug-ncurses@gnu.org.
This page was obtained from the tarball ncurses-6.6.tar.gz fetched
from ⟨https://ftp.gnu.org/gnu/ncurses/⟩ on 2026-01-16. If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for the
page, or you have corrections or improvements to the information
in this COLOPHON (which is not part of the original manual page),
send a mail to man-pages@man7.org
ncurses @NCURSES_MAJOR@.@NCU... 2025-01-18 form_fieldtype(3X)
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HTML rendering created 2026-01-16 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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